The Three Treasures
Here is something for probably the more advanced students of Tai Chi and Chi Kung who come along to the studio. The Three Treasures otherwise known as Jing, Chi and Shen or Essence, Energy and Spirit can be broken down into their individual components as Jing (essence), the energy we are born with, closely associated with the water element and the kidneys - Chi (energy) is what it says energy and how we use it while Shen can be spirit, not spirit in the sky spirit but how we are - when our Jing and Chi are strong it shines through making us feel and look healthy and strong.
A better description can be used by comparing the three treasures to a candle - The essence would be the wax and wick of the candle which makes it substance and Chi could be likened to the flame which will be strong if the main body of the candle is good. Shen (Spirit) would be the light that glows from the flame - the better the essence, the stronger the flame and the brighter the spirit (the glow around the flame) - I find this to be a really good analogy.